Soybean protein extract

Abstract

A recovered soybean protein extract is disclosed containing at least 55 percent of soybean protein, on a dry solids basis, and from 2 to 32 percent of natural soybean oil, based on the weight of the protein. The remainder of the extract includes water, carbohydrates, minerals and proteinate salts. A method for recovering the soybean protein extract, whereby the oil and the protein are jointly separated from the soybean, is also disclosed. The method involves grinding cleaned and dehulled soybeans, slurrying the ground product in peroxide and water, and recovering a protein extract from the slurry by centrifugal processing. An isolate, protein content at least 85 percent, is obtained by adjusting the slurry pH to at least about 8 to solubilize the protein, removing the insolubles and free oil, and then precipitating the protein solids by lowering the pH to about 4.5; the precipitated protein is then recovered from the slurry. The protein and oil content of the extract may be varied through minor modifications to the above steps so as to produce oil-containing extracts having as low as 55 percent protein. Unexpectedly, the protein extract of the instant invention, notwithstanding an oil content of at least 2 percent, has been found to have an extended shelf life.

What we claim is: 
     
       1. A soybean protein extract containing at least 55 percent of soybean protein, on a dry solids basis, and from 2 to 32 percent of natural soybean oil, based on the weight of the protein, and the remainder of said extract consisting essentially of carbohydrates and minerals, and edible proteinate salts of the protein of said extract, said oil and said protein being further separable from each other by solvent extraction and having been jointly separated from soybeans by the method including the steps of: (a) dry grinding such soybeans to a ground product finer than 70 mesh, U.S. Sieve Series;   (b) agitating said ground product as a slurry in an alkaline aqueous solution at a pH of at least about 8 for a time sufficient to solubilize protein and to yield aqueous, oil, and insoluble solids phases;   (c) separating said aqueous and oil phases from said insoluble solids phase; and   (d) either first centrifugally separating said aqueous phase from said oil phase and then lowering the pH of said aqueous phase to 4.0-5.0 to precipitate such protein extract, or first lowering the pH of said combined aqueous and oil phases to 4.0-5.0 to precipitate such protein extract and then centrifugally separating out such extract from said oil phase.   
     
     
       2. A soybean protein extract as claimed in claim 1 wherein the oil content is from 2 to 15 percent. 
     
     
       3. A soybean protein extract as claimed in claim 2 wherein the soybean protein content is at least 85 percent.